Experimental studies are under way for the concurrent exposure of appropriate biological targets to numerous carcinogens of different classes, each administered at doses which would be expected to produce marginal or undetectable effects in the chosen system. Quantitative exposure/response studies are addressed to testing the hypothesis that many different carcinogens can act synergistically to induce a significant level of carcinogenic response when given concurrently at individually ineffective doses. Mechanisms of action will be studied to determine the most effective conditions of synergism. The biological models selected for these studies include in vitro assays for mutagenesis and neoplastic cell transformation and whole animal models. Analysis of dose-response relationships in carcinogenesis is conducted on data collected in a comprehensive literature survey. Dose-response data are obtained experimentally in the selected biological systems.